Bacon, and one who in later days has successfully followed him on this ground, point out as one of the most important subjects of human inquiry, equally necessary to the science of morals and of medicine, "The history of the power and influence of the imagination, not only upon the mind and body of the imaginant, but upon those of other people."

As for the reciprocal knowledge, which is the operation of the conceits and passions of the mind upon the body, we see all wise physicians, in the prescriptions of their regiments to their patients, do ever consider accidentia animi, as of great force to further or hinder remedies or recoveries: and more specially it is an inquiry of great depth and worth concerning imagination, how and how far it altereth the body proper of the imaginant; for although it hath a manifest power to hurt, it followeth not it hath the same degree of power to help.